Telephone system



Jufly "R6, 1935. H. HOVLAND 2,8,2M

TELEPHONE SYSTEM Filed April 20, 1954 2 Sheets-Sheet 1 DIFFEREN TML MARGINA L VER 7.- STEP R0 7. STEP FIG.

MARG/NAL lNl/ENTOR By H. HUI/LAND A 7 70 NEV 1935. H. HOVLAND 2,@ ,281

' TELEPHONE SYSTEM,

Filed April 20,- 1954 2 Sheets-Sheet 2 FIG. 2

INVENTOR H. HUI LAND ATTOR 5r Patented July 16, 1935 UNITED STATESPATENT OFF ICE TELEPHQNE SYSTEM Application April 20,

9 Claims.

This invention relates to telephone systems and particularly to thoseinvolving party lines equipped for message register service.

Its objects are to secure improvements in the identification of acalling station on a party line, to guard against the inaccuratecharging of calls made by the different subscribers, to enable a test ofthe identifying equipment on every call, and to otherwise improvesystems of this kind.

A feature of the invention is a party-line system in which anidentification device, such as a space-discharge tube, is provided atone of the stations, together with means at the central office forconnecting a source of identification current to the line, when a callis made, to determine the presence or absence of said tube, and in whicha test is made after the calling party has replaced his receiver todetermine whether or not said identification device is in operativecondition. In this way it is possible to determine the accuracy of theidentification test, which assumes that the tube or other device is inoperative condition, since the subsequent test for operativeness is madewhen all receivers are on the switchhooks, at which time it isdefinitely known that the tube is connected in circuit with the line.

Another feature is an arrangement in which one of the registers of atwo-party line is connected to the sleeve conductor and the otherregister to one of the talking conductors, and in which the latterregister is selectively connected to the line for operation by means ofthe line relay. Since it is desirable to have the register disconnectedfrom the talking conductor during conversation, this is accomplished byholding the line relay operated to hold open the register circuit. Atthe end of conversation, dependent on which party made the call, eitherthe register on the sleeve is operated or the line relay is released toclose the circuit to the register on the talking conductor, followingwhich this latter register is actuated. In this case, it is necessary tohold the cut-off relay operated to prevent thesubscriber fromreoperating the line relay and thus disconnecting the register before itis operated.

These and other features of the invention will be more clearlyunderstood from a consideration of the following detailed description,which should be taken in conjunction with the accompanying drawings, andalso from the appended claims.

The drawings comprising Figs. 1 and 2, disclose a portion of astep-by-step dial system in which the invention is embodied.

Fig. 1 diagrammatically represents two subscribers stations J and Wconnected by a com- 1934, Serial No. 721,513

mon line Hill to terminals in one bank of the line-finder switch. Thisline-finder LF has two banks and two sets of brushes. The lines of onegroup, including line I00, are connected to terminals in one bank(upper) to which the brushes H5, H6 and Ill have access; and the linesof the other group (none shown) are connected to terminals in the otherbank (lower) to which the brushes I I8, I I9 and I26 have access.Whenever a call is originated over a line to which the line-finder hasaccess, a ground is connected to the commutator segment corresponding tothe level in which the term nals of this line are located. This groundconnection is controlled by the single group relay l 1'33 for all of thelines connected to the terminals of that level of both banks.

Since but one set of two sets of brushes has access to the terminals ofa particular line, the required set of brushes must be renderedeffective, to the exclusion of the other set, at or before the findingof the terminals of the calling line. To this end the aforementionedgroup relay is arranged to connect the corresponding commutator segmentto ground through resistance 5M if the calling line is connected toterminals in the upper bank, and to connect the segment directly toground if the calling line is connected to terminals in the lower bank.

Fig. 2 shows a trunk circuit T-l and a first selector S for extendingthe connection to a called station (not shown) through a second selector(not shown) and connector (not shown) in the well known manner. Thetrunk circuit T-l is individual to the line-finder LF, shown in Fig. 1,and to the selector S. The line-finder and selector are of the wellknown Strowger type, but the invention may be applied to systems usingother types of switches.

The subscribers set at W, known as the ring subset, is equipped with anidentifying space-discharge tube T, so arranged that the removal of thereceiver from the receiver hook disconnects the tube from the associatedline. This tube may be of any desirable construction and may be chargedwith any suitable substance such as neon. The subscribers set at J,known as the tip subset, is not equipped with a space-discharge tube.Each station is also equipped with a dial for controlling the operationof the switches used in extending a connection to the called station.

The line-finder switch is equipped with two banks and two sets ofbrushes similar to the switch disclosed in Patent 1,809,124, issued toHovland on June 9, 1931, but the associated circuit is somewhatdifferent from that shown in the patent to Hovland. Upon the originationof a call at ei her of stations J or W of line I08, the line-finder LP(or, if this line-finder is busy, some other line-finder to whoseterminal bank the line tilt; is multipled) is effective to associate theproper set of brushes with the terminals to which the line is connected.The calling line is thereby extended to the trunk circuit which servesto connect the line-finder with its associated selector S.

The trunk circuit T--i is arranged in accordance with this invention toidentify the calling station on a two-party line and to operate themessage register which is individual to the calling station. In order todetermine the accuracy of the first or identification test, twosubsequent tests are applied to the calling subscribers line. The firstor identification test is applied after the first digit has been dialed,whereupon the test battery is connected to the tip and ring conduc torsof the calling line through the test relay 2% to detec the presence orabsence of the spacedischarge tube T and thereby identify the call ingsubscribers station. Thus, if the call originated at station J, theaforementioned battery will beirnpressed across the electrodes of thespace discharge tube T, associated with station W, thereby causing thesaid tube to ionize and become sufficiently conductive to provide anoperating circuit for test relay 2136. If the call originated at stationWjthe space-discharge tube is disconnected from the circuit, when thereceiver at the calling station W is removed from the receiver hook, andconsequently the test relay 200 does not have an operating circuit.

The second test is made, after the calling subscrib-er disconnectsfollowing a completed call, to determine whether there is a resistanceleak of excessive conductivity from the line conductors of the callingline, to ground. This test is made byconnecting the negative pole of thecentral oiiice battery to the tip and ring conductors of the callingline through the winding of relay i. This voltage is not sufficient toionize the tube T, but, if a leak of sufficient conductivity existsbetween the line conductors and ground, relay Zili will operate andprevent subsequent registration. If the leak test is satisfactory, asindicated by the non-operation of relay iili, a third test is initiated,to determine whether or not the space-discharge tube T is in operativecondition. This test follows the second test and is made byreassociatingthe test relay 2% with the tip and ring conductors of thecalling line. The test relay if operated under this condition, indicatesthat the space-discharge tube is function-- ing satisfactorily; but, ifrelay 280 fails to operate, an unsatisfactory test results andsubsequent operation of the message register associated with thesubscribers line is blocked. These operations are best explained by adetailed description of the operation of the circuits shown in thedrawing.

Assume that a call is originated by the removal of the receiver from thereceiver hook at either of stations J or W, that brushes Iii), lit andIll are associated with lines terminating in the upper group and thatbrushes Mil, H9 and Hill are associated with lines terminating in thelower group. Line relay lei operates in an obvious circuit over the linewe thereby connecting its lower winding in parallel with the winding ofthe cutoff relay in! and in parallel with tip party (J register 522 tothe sleeve terminal associated with line i lilin the bank of line-finderLF; line relay I!!! connects the ring conductor of line I 00 toconductor 523 and also closes a circuit for operating group relay I63,from ground at the'back contacts of the cut-01f relay I {12, through theupper inner front contact of relay I D I, resistance IM, and through thewinding of group relay I03 to battery.

In operating, group relay I03 closes a circuit from ground through itslower front contacts, over conductor I05, through the upper backcontacts of relay E06, back contact of vertical magnet I01,

normally closed contacts of the 10th vertical step springs, winding ofrelay I I2, back contact of rotary magnet I98, closed contact of the10th rotary step springs, and through the lower back contact of relayI06 to battery. The closing of this circuit is effective to operate theinterrupter relay I I2. Relay I I2 closes a circuit from ground throughits front contact, the upper outer back contact and lower winding ofrelay I I0, and through the winding of vertical magnet ID! to battery.The vertical magnet I0! is thereby operated to advance the shaft andbrushes of the line-finder LF up to the first level; but relay H0 isslow to'operate and does not operate on the pulses of current throughits winding during the vertical movement of the switch. The verticaloff-normal springs VON are actuated when the shaft is advanced out ofits normal position thereby connecting' ground toconductor I I3. Theoperation of magnet I01 also opens the circuit through the winding ofrelay H2, thereby causing the release of relay I I2. The release ofrelay 3 I 2 opens the aforementioned circuit through the lower windingof relay I Hi and winding of vertical magnet Illl', thereby causing therelease of magnet I07. The release of magnet I0! again closes thecircuit through the winding of relay II2. Thus interrupter relay H2 andvertical stepping magnet I01 alternately operate and release to advancethe shaft andbrushes of line-finder LF until the level of the callingline is reached.

Let it be assumed that line I 00 is connected to terminals in the firstlevel of the upper bank and that the aforementioned operation of grouprelay M13 is effective to connect ground through the upper outer backcontact of cut-off relay I02, the upper inner front contact of relay I0I, resistance set, and through the upper front contact of relay I03, tothe first segment of commutator C.

When the shaft and brushes have been advanced to this level, a circuitis closed from the grounded first segment of commutator C, throughcommutator brush I4, upper winding of relay I09, winding of relay II2,back contact of rotary magnet I08, closed contacts of the 10th rotarystep springs to battery at the lower back contact of relay I96. Relay H2is held operated in this circuit even though the vertical magnet I07 hasopened its backcontact; but relay I09 is marginal and does not operateat this time. Belay H2 maintains the operation of vertical magnet I0'Iin a circuit including the lower winding of relay MD as aforementioned.This circuit is closed for a sufficient length of time to partiallyoperate slow-temperate relay IIE. Relay H0 is energized sufficiently tooperate its inner upper front contact and thus close a circuit fromground at upper contacts of VON springs, upper inner front contact ofrelay 'I I0, thence in parallel, one

path extending through the upper winding of relay H0 to battery at thelower back contact of relay I06, and the other extending throughresistance I2I and upper winding of relay III to battery. Relay H0 iscompletely operated in this circuit; but relay III is marginal and doesnot operate at this time. Relay I I0 opens the circuit through thevertical magnet thereby causing its release. The release of magnet I0Iagain closes the circuit through the winding of relay I I2, overconductor I05 to the ground at group relay I03. In case the calling lineis connected to terminals on the tenth level, the circuit through thewinding of relay I i2 is maintained through the lower front contact ofrelay I I0, instead of through the 10th vertical step springs. Relay II0 also closes a circuit for operating the rotary magnet I08; thiscircuit may be traced from battery through the winding of magnet I08,the upper outer front contact of relay IIO, front contact of relay II2to ground at the lower inner back contact of relay Ill. The operation ofthe rotary magnet advances both sets of brushes into engagement with thefirst set of terminals in the previously selected level. Since themarginal relay I09 was not operated, brushes H5, H6 and III areeffective on the call in question to the exclusiontof brushes H8, H8 andIE0.

If the calling line is not connected to the first set of terminals inthe selected level, the sleeve terminal tests busy or idle, dependingupon whether the line associated therewith is busy or idle; but ineither case the interrupter relay H2 is released by the operation ofrotary magnet I 08. The release of relay I I2, opens the circuit throughthe winding of magnet I00. The release of mag- I 08 again closes thecircuit for operating relay H2; and the reoperation of relay II2 closesthe circuit for reoperating magnet I08. Thus the interrupter relay I I2and the rotary stepping magnet alternately operate and release toadvance the brushes successively from one set of terminals to the nextuntil the terminals of the calling line are reached.

When brush I i 5 makes contact with the sleeve terminal of the callingline, relay H2 is held operated to prevent further advance of thebrushes; the circuit for holding relay II2 may be traced from batterythrough the winding of relay I02, in parallel with the lower winding andfront contact of relay IOI, and in parallel with the Winding of registeri222, sleeve terminal and brush II5, conductor I25, upper middle backcontact of relay I06, lower winding of relay III, front contact ofmagnet I03, winding of relay II2, lower front contact of relay I backcontact of magnet I01, back contact of relay I00, and over conductor I05to ground at contact of group relay I03. This circuit is also effectiveto operate the cut-off relay I02; to operate relay III; and to holdrelay IOI operated. The tip party (J) register I22 is marginal and doesnot operate at this time. The current through the lower winding of relayIII electromagnetically aids the current flowing through its upperwinding sufiiciently to close the upper inner front contact of saidrelay and thus close a circuit from battery through its upper winding,hold conductor 2I0, lower outer back contact of relay 2%, sleeveconductor 209, to ground at upper middle front contact of relay Ill; theenergization of the upper winding of relay iII causes the completeoperation of this relay. If, during the rotary advance of the switch,the sleeve brush IIE encoimters a busy sleeve terminal, on whichbooster-battery is being applied, for the purpose of operating thesubscribers register, the current through the lower winding of relay iIIelectromagnetically opposes the current flowing through its upperwinding and thereby prevents a 'falseoperation of relay III. i

- The aforementioned operation of cut-off relay I02 disconnects theconductors of line I00 from the windings of line relay IEIi but relayIOI does 1- notrelease since its holding winding is energized inparallel with the winding of the cut-off relay I02. The operation ofrelay I02 also opens the circuit through the winding of group relay I03,and the release of relay I03 disconnects the ground from start conductorI05. With brushI I5 in contact with the sleeve terminal of line I00 thepotential is such as to indicate that the line is busy and to preventany other hunting switch or connector from stopping on the terminals ofthis line.

The complete operation of relay III extends the connection from line I00through its upper front contacts to the winding of relay 206 and thencethrough the windings of line relay 205 of selector S. The circuit foroperating relay 205 may be traced from battery through its upperwinding, upper outer back contact of relay 208, upper winding ofpolarized relay 206, upper outer back contact of relay 203, ringconductor 220, upper outer front'contact of relay I I I, upper middleback contact of relay I09, brush H6 and ring terminal of line finder LF,conductor I23, upper outer front contact of line relay IOI, ringconductor of line I00, through the calling subscribers instrument, backover the tip conductor of line I00, through tip terminal and brush In oflinefinder LF, upper inner back contact of relay I09, upper next toouter front contact of relay III, tip conductor 22I, lower outer backcontact of relay lower winding of polarized relay 206, upper inner backcontact of relay 208, lower winding of relayv 205, upper normally madecontact of llth rotary step springs, and through left winding of dialtone transformer 222 to ground. Relay III also releases the rotarymagnet I08, closes an obvious circuit for operating relay I06 andconnects a direct ground to sleeve conductor I25 for holding the linerelay IIlI and cut-off relay I02. This circuit may be traced from sleeveconductor I25, upper next to inner front contact of relay I l I toground at the upper middle front contact of relay I I0. Relay 205operated as aforementioned causes the operation of slow-to-release relay20'! in a circuit traced from ground at the lower outer back contact ofrelay 208, front contact of relay 205, and through winding of relay 201to battery. Relay 20'! connects a holding ground to sleeve conductor 209and to hold conductor 2I0 so as to hold cut-off relay I02 and relay IIIrespectively and independently of the ground at the upper middle frontcontact of relay IIO. This circuit may be traced from ground at upperfront contact of relay 207, conductor 2I'I, back contact of relay 2I8 tohold conductor 2I0 and through lower back contact of relay 204 to sleeveconductor 209.

Relay I06, operated as aforementioned, opens the circuit through upperwinding of relay I I0 and opens the circuit through the winding of relayI I2 thereby causing the release of said relays. With relay I06operated, the start conductor I05 is extended through the upper innerfront contact of relay I06 to conductor I26 which leads to thenextline-finder in the'group.

If a call is originated over a line connected to terminals in the lowerbank associated with the lower bank of the switch it is necessary thatrelay I be operated in order to associate the brushes II 8, H9 and I20with the terminals of lines terminating in this group. The initiating ofa call for a line, terminating in the lower bank, causesthe operation ofgroup'relay I03 as aforementioned. The line relays (not shown), for thelines associated with the lower bank of terminals are wired so that theaforementioned resistance m4 is not included in the circuit foroperating group relay m3. Consequently, when the commutator brush 44makes contact with a commutator segment, associated with the properleve1,'the current through the upper winding of relay 509 is sufficientto operate this relay so as to render brushes l 68, l [9 and I20effective to the exclusion of brushes H5, H0 and Ill. Relay I09 locksthrough its lower winding and front contact, over conductor M3, toground at the upper front contact of VON springs.

When the subscriber at the calling station dials the first digit of thenumber of the called station the line relay 2535 of selector S isalternately released and reoperated each time the subscribers line loopis opened and closed at the dial. When the line relay 28% of selector Sreleases, a circuit is closed from battery, through the wind ng of thevertical stepping magnet 2! I, winding of relay 252, lower front contactof relay 201, back contact of relay 205 and through the lower outer backcontact of relay 208 to ground. The magnet 2 i l and relay 2l2 bothoperate in this circuit. Relay M2 is a slow-to-release relay and remainsoperated until all of the impulses corresponding to each digit have beenreceived. Relay 2B! is also slow to release and holds during the receipti this train of impulses. The operation of magnet Zil steps the shaftand brushes of selector S up to the first level of bank terminals. Thereoperation of relay 205 releases the magnet 2| l, and each successiverelease and reoperation of relay 205 causes the operation and release ofmagnet 21 l. The shaft and brushes of the selector are raised in thismanner, step-oy-step, to the level through which the call may beextended toward the called station.

As soon as the shaft of selector S is moved. olfnormal the verticaloff-normal springs VON are actuated and when relay 2 l2 operates ashereinbefore described, a circuit is closed, for operating relay 263,from cattery through the winding of relay its, upper contact of the VONsprings, front contact of relay 2|2 to ground at upper front contact ofrelay 201. Relay 2 l2 also closes a circuit for operating relay 2 I4from battery through the winding of relay 2 l4, front contact of relayM2 to ground at the upper front contact of relay 207. Relay 2 I4 closesan obvious operating circuit for relay 215. Relay 213 looks in a circuitfrom battery through its winding and the upper contact of VON springs,through the back contact of rotary magnet'2l6, upper front contact ofrelay 2 l3 and through the lower outer back contact of relay 2518 toground.

When all of the impulses originated by the dialing of the first digit ofthe called number have been received, the release of relay 2 if! ofselector S opens the circuit for relay 2 [4/ Relay 214 released closes acircuit for operating relay 203 to initiate the identification test.This circuit may be traced from ground at upper outer back contact ofrelay 25%, front contact of relay 2 l5, upper inner back contact ofrelay 219 and through the winding of relay 2&3 to battery. Relay 2M alsoreleases relay 2 l 5 but the latter is slow to release and remainsenergized, after its operating circuit is broken, for a sufficientlength of time to complete the identification test. In operating, relay203 (a) transfers the tip and ringc'ondu'ctors 22! and 220 from thewindings of relay 205 to the winding of identification test re1ay'200,and (b) closes a circuit for. holding line relay 205 of selector S. Thislatter circuit is traced from ring conductor232, upper winding of relay206, upper inner front contact of relay 203, through resistance 223,upper outer back contact of relay 2|9, lower winding of relay 206 to tipconductor 233. The release of relay 203 disconnects the identificationtest relay from the tip and ring conductors HI and 220 and restores thecontinuity of these conductors.

If the call originated at station J (tip party), the identification testrelay operates, during the time that its winding is connected toconductors 22l and 220 in a circuit traced from battery, lamp 224,resistance 225, winding of identification test relay 200, back contactof relay 202, upper back contacts of relay 204, front contacts'of relay203, over conductors HI and 220, through'thefront contacts of relay I Il line-finder brushes 5 H and I I6 over the tip and ring conductors ofline I00 and through the space-discharge tube T, at station W, to groundthrough the ringer. The voltage applied across the tube, by the circuitjust traced, is suificient to ionize said tube, thereby rendering itsufficiently conductive so that the resulting current flowing in thecircuit operates relay 200. If, however, the call originated at stationW (ring party) relay 200 does not operate.

for there is no identification tube at station J and the identificationtube T at station W is rendered ineffective, when the receiver at thelatter station is removed from the receiver hook. If relay 200 operatesrelay 226 also operates, in a circuit traced from ground at the frontcontact of relay 200, lower innerback contact of relay 2|8'and throughthe Winding of relay 226 to battery. Relay 226 looks in a circuitthrough its upper inner front contacts, upper middle back contact ofrelay'2l8, to ground on conductor 2 ii.

The release. of relay 2l2 of selector S, after the dialing of the firstdigit, is also eifective to close a circuit for operating the rotarystepping magnet 2|6; this circuit may be traced from bat tery throughthe winding of magnet 22 lower front contact of relay 213, normallyclosed contact of relay 2I2 to ground at upper front con- The rotarymagnet 2|6 rotact of relay 201. tates the shaft of selector S one stepso that the brushes 228, 229 and 230 make contact with the terminals ofthe first trunk in the, previously selected level. The operation of therotary magnet causes the release of relay M3. The release of relay 2|3causes the release of the rotary magnet. The release of magnet 2H5closes a circuit from battery through the winding of relay 2 [3, uppercontact of the VON springs, back contact of magnet 2l5, conductor 23!,winding of relay 208, lower closed contact of 11th rotary step springsto ground at relay 207. Conductor 215i is also connected through thelower inner back. contact of relay 208 and the sleeve brush 220 to thesleeve terminal of the first trunk in the selected level. If this trunkis idle relay 208 operates and relay 2| 3 does not operate; but if thetrunk is busy the winding of relay 208 is short circuited by ground (notshown) at sleeve terminal 227 so that relay 2| 3 operates and relay 208does not operate. The reoperation of relay 21 3 causes the reoperationof the rotary stepping magnet 2l6. The alternate operation and releaseof relay M3 and magnet 2H5 advance the brushes of selector S step bystep from one set of terminals to the next.

When an idle trunk is encountered relay 208 operates in series withrelay 2E3; but relay 2| 3 is marginal and does not operate. Relay 208disconnects the tip and ring conductors 233 and 232 from the windings ofline relay 205 and extends these conductors through brushes230 and 229over the tip and ring conductors of the selected trunk to the windingsof the line relay in the second selector circuit (not shown). Relay 208also establishes a temporary busy condition on the sleeve terminal ofthe selected trunk by connecting the sleeve conductor 211 through thelower inner front contact of relay 208 and brush 228 to the sleeveterminal 22?. Relay 205 releases thereby causing the release of relay231. Relay 201 is slow to release so that the ground at its upper frontcontact is not disconnected from sleeve conductor 2!! until sufficienttime has elapsed for the operation of the line relay of the secondselector (not shown) to have been effective to cause a permanent groundto be connected from sleeve terminal 221, through brush 228, and thelower inner front contact of relay 283, to sleeve conductor 2V1.

If all trunks in the selected level are busy the selector, upon reachingthe 11th rotary step, actuates 11th rotary step springs therebydisconnecting transformer 222, which supplies the usual dial tone, fromthe lower winding of relay 205 and connecting thereto transformer 239,which furnishes a distinctive audible signal to indicate a trunks busycondition to the calling subscriber.

.When the remaining digits of the called stations number are dialed bythe calling subscriber, the second selector (not shown) and connector(not shown) are operated in the usual manner to extend the connection tothe called subscribers line.

Assume that the called line is idle when connection is establishedtherewith, that ringing potential is connected to the line, that thesubscriber at the called station answers and that the call is onefor'which the calling subscriber should be charged. When the receiver isremoved from the receiver hook at the called station, the source oftalking current at the connector (not shown) for the calling subscribersline is reversed, with respect to the tip and ring conductors of theline in the usual manner, so as to operate the polarized supervisoryrelay 2% in the'trunk Tl.

'The operation of the supervisory relay 20$ closes a circuit foroperating relay 2); this circuit may be traced from battery through thewinding of relay 2E9, front contact of relay 2%, lower back contact ofrelay M9 to the brush of interrupter 234. When the brush ofinterrupter234 is connected to ground relay 219 operates and looks through thefront contact of its makebefore-break springs to ground. Relay 21sdisconnects its initial operating ground at the brush of interrupter 23i and closes a circuit for operating relay 2l3, from the brush ofinterrupter 235, lower front contact of relay 2m, and through upperinner back contact and winding of relay 218 to battery. When the brushof interrupter 235 is connected to ground relay 2E8 operates and locksin a circuit traced from ground at its lower outer front contact, upperouter back contact of relay 236 and through upper inner front contact ofmake-before-break springs and winding of relay 2 l8 to battery.Interrupter 235 isso timed with respect to interrupter 234 that a timeinterval of not less than two seconds elapses from the time ground isconnected to the brush of interrupter 234 until ground is connected tothe brush of interrupter 235. The closed period for both interrupters isapproximately 0.5 second. This time delay is introduced to prevent afalse indication of the charging operation if supervisory relay 2% ismomentarily operated due to trunk or line busy signal. Relay 2! alsoprovides a. second locking circuit for relay 2 l9. This circuit istraced from lower. next to outer front contact of relay 2l8 through thewinding of relay 2!!! to battery. With relay 2H3 operated, sleeveconductor 2|! is disconnected from the sleeve conductor 209 and holdconductor 2H3, at the upper middle back contact of relay 2l8 and isconnected to relay 2! at the upper outer front contact of relay 2E8;sleeve conductor 229 and hold conductor 2 H! are connected to ground,through retardation coil 23'l, at the make spring of the upper middleinake-before-break springs of relay 2 I8. Relay 2M is energized fromground on sleeve conductor 21? and in turn energizes slow-to-releaserelay 2E5 in an obvious circuit. Condenser 223 and retardation coil 231,associated with the sleeve conductors 2H and 209 of the selector S andtrunk circuit Tl are furnished to provide a suitable path for thetransmission of th'eusualnumber checking tone.

. When the calling subscriber replaces the receiver on thereceiver'hook, the line relay of the connector (not shown) releases. Theconnector switch and associated second selector (not shown) are returnedto normal in the usual manner. When the sleeve ground is disconnectedfrom the sleeve terminal 221 with which brush 228 is in contact, relay298 of selector S and relays 2M and 206 of trunk Tl are released. Therelease of relay 208 closes a circuit for operating the release magnet240 and selector S is returned to normal in the usual manner. Inreleasing, relay 2M closes a circuit to momentarily operate relay 202for initiating the conductance test of the calling subscribers line.This circuit may be traced from ground at the upper outer back contactof relay 2| 4, front contact of relay 215 upper inner front contact ofrelay 2 l9 and through the winding of relay 202 to battery. This test ismade to determine the presence or absence of a resistance leak fromeither the tip or ring conductors of the calling subscribers line toground. The necessity for this test resides in the condition, whereinthe ring party (W) initiates a call and wherein said leak is ofsufficient conductance to cause the operation of aforementionedidentification test relay 2G0 and thereby identify the tip partlyerroneously. Belay 2&2 operates relay 203 in an obvious circuit andconnects the test relay?! to tip and'ring conductors 22! and 228respectively. This circuit may be traced from battery through winding ofrelay 29 l upper outer front contact of relay 2G2, upper back contactsof relay 204, front contacts of relay 2113 to conductors 22! and 22!!and thence over the tip and ring conductors of the calling subscribersline as aforementioned. The battery potential applied to the line Hit,in this case, is not sufiicient to operate the space discharge tube T.If either the tip or ring conductor of line it!) presents aresistanceleak to ground of excessive conductivity relay 20! willoperate in the circuit just traced. However, if the line Elli) presentsa resistance leak to ground of normal conductivity relay 2% will notoperate. If relay 28% operates it closes an the trunk circuit T-l willproceed to operate obvious locking circuit for relay 202 therebypreventing the subsequent release of thetrunk TI from subscribers lineI00. The trunk circuit T-I is so arranged that if its release is noteffected within a fixed time, starting from the time the conductancetest is initiated, the alarm circuit (not shown) will function toattract the attention of the maintenance force. The circuit forinitiating said alarm is traced from ground. at the upper inner backcontact of relay 2I4 and through lower middle front contact of relay?.I8 to the alarm circuit.

To proceed with this description we will assume 7 that the leak test issatisfactory. Slow-to-release relay 2 I5 releases thereby causing therelease of relay 262. Relay 203 however remains operated in a circuitthrough its lower inner front contact to ground at the lower outer frontcontact of relay ZIB. The release of relay Z02 reconnects theidentification test relay 200 to the tip" and ring conductors 22I and226 in an aforementioned circuit, for applying the third test. This testis made to determine whether or not the space discharge tube T is inoperative condition and is made immediately after the leak test at atime when the receivers at both the tip and ringstations are on theirrespective receiver hooks as aforementioned.

If the said identification tube T is operative test relay 2% willoperate as aforementioned and the proper meter associated with thecalling subscribers line; but if the test is not satisfactory test relaywill remain non-operated and the trunk in this case will preventregistration and will cause the alarm circuit to function in anaforementioned manner. The necessity for this test resides in thecondition wherein the tip party initiates a call and wherein the spacedischarge tube T is not in an operative condition. The identificatontest in this case should have caused the operaton of identification testrelay 200 thereby identifying the tip party; but with said tube inanon-operative condition said test relay remains ncn-operated therebyindicating the ring party erroneously. Thus the accuracy of theidentification test is assured by the operation of test relay 200.

As to the operation of the meters associated with the two-party lineI00; first the operation of the ring party (W) register will bedescribed followed by a description of the operation of the tip party(J) register. The operation of relay 200 causes the operation of relay264 in a circuit traced from groundat the front contact of relay 20d,lower inner front contact of relay 2I8 and through winding of relay 204to battery. Relay 204 looks through its lower inner front contact toground at the lower outer front contact of relay 256. The short circuitacross resistance 24! at the lower outer back contact of relay 204 isopened by the operation of relay 204 and resistance E li is included inseries with sleeve conductor 206. This circuit may be traced from sleeveconductor 209, upper outer back contact of relay 226, resistance 24Lupper middle front contact of relay 2 I8 and through retardation coil23? to ground. The resistance'introduced into the aforementioned sleevecircuit causes the release of line relay IllI but does not affect thecut-off relay I02. Relay I ElI released disconnects conductor i23 fromthe ring conductor of line I00, to prevent the initiation of anothercall until the register has operated, and connects the register :24thereto, thereby closing a circuit for the operation of relay 236. Thiscircuit may be traced from battery through winding of register I24,upper back contact of relay IOI, ring terminal and brush II6 of theline-finder LF, upper middle back contact of relay I09, upper outerfront contact of relay II I, ring conductor 220, upper outer frontcontact of relay 203, upper outer front contact of relay 204, uppermiddle back contact of relay 226, lower back contact of relay 236, lowerback contact of relay 226, and through upper winding and upper innerback contact of relay 236 to ground. The provision for operating relay236 in series with register I24 is made for the purpose of testing therelease of line relay I0i. If said line relay fails to release in serieswith resistance 24I as aforementioned relay 236 will not operate, thetrunk T-I will be held'and an alarm will be effected, as aforementioned.Relay 236 (a) locks in a circuit traced from battery through its lowerwinding and upper next to inner front contact to ground at the lowerouter front contact of relay 2I8; ((2) opens the aforementioned lockingcircuit for slow-to-release relay 2I8; (c) connects a direct ground tothe sleeve conductor 209, toguard against seizure by either anotherline-finder or connector, in a circuit traced from ground at upper nextto outer front contact of relay 236, upper outer back contact of relay226 to sleeve conductor 209; and (d) connects booster-battery to thering conductor 220 for the purpose of operating the ring party (W)register I24. This circuit may be traced from. booster-battery, throughlamp 242, resistance 243, front contact of relay 236, upper back contactof relay 226, upper outer front contact of relay 204, upper outer frontcontact of relay 203 to ring conductor 220 and thence through theregister I24 to battery over an aforementioned circuit.

Having described. the operation of the circuit to effect registrationwhen the ring party (W) initiates a call, a description will now be madeof the operation of the'circuit to effect registration when the tipparty (J) initiates a call. As aforementioned, relay 226 is operated andlocked when the identification test relay 200 identifies the tip party(J). The operation of the circuit, following the subscribers replacementof the receiver on the receiver hook, is the same as described for thering party (W) up to the point where relay 204 operates. Since the tipparty (J) register I22 is associated with the sleeve circuit of theline-finder LF, by the line relay IOI, it is not necessary to releaserelay IOI during the registration period. The line relay IOI is heldoperated in a circuit traced from ground through winding of retardationcoil 231, upper middle front contact of relay 2I8, lower front contactof relay 226, lower back contact of relay 236, upper next to inner frontcontact of relay 226 to sleeve conductor 269 .and thence through theWinding of relay I0! in an aforementioned circuit. Relay 204 operatedcloses a circuit for operating relay 236 from ground at the lower frontcontact of relay 2I8, lower middle front contact of relay 204, uppernext to outer front contact of relay 226 and through the lower windingof relay 236 to battery. Relay 236 disconnects ground from the sleeveconductor 209 and connects booster-battery thereto to operate the tipparty (J) register I22. This circuit may be traced from booster-battery,through lamp 242, resistance 243, front contact of relay 236, upper nextto inner front contact of relay 226, to sleeve conductor 209 and thencethrough the winding of register I22 in parallel branches extendingthrough contacts of relays I Ill and I 02. Relay 236 also opens theholding circuit for relay 2I8 thereby causing its release.

Relay 2I8 is slow to release and is designed so that it will remainoperated for a sufficient length of time, after its holding circuit isopened, to efiect registration. This relay releases, following theoperation of relay 236 as aforementioned, thereby releasing relays 2I9,203, 204 and 236. Relay 236 removes ground from the hold conductor 209;releases relay 226, if operated; disconnects booster-battery from thesleeve conductor 209 (for tip party registration) disconnectsbooster-battery from the ring conductor 220 (for ring partyregistration) and disconnects ground from the sleeve conductor 269 (forring party registration). The trunk circuit T-I is thus released and allapparatus is restored to normal. The disconnection of eitherbooster-battery, or ground from sleeve conductor 209 causes the releaseof line relay IOI (if operated) and cut-off relay I02 thereby restoringthe subscribers line circuit to normal. The disconnection of ground fromthe hold conductor 2I0 releases relay III of the line-finder LF. RelayIII released closes a circuit for operating the release magnet I28; thiscircuit is traced from ground at the lower outer back contact of relay II I, upper outer front contact of relay I06 and through the Winding ofrelease magnet I28 to battery. The operation of magnet I28 causes theshaft and brushes to restore to normal. With the VON springs thusrestored to normal position ground is disconnected from conductor II3,thereby releasing relay I09. Relay III also opens the circuit throughthe upper winding of relay I06 thereby causing the release of relay I06unless said relay is held operated through its lower winding and upperinner front contacts to ground on starting conductor I05; thus relay I06can not release it starting conductor I05 is grounded due to theorigination of another call until the calling line has been found bysome other line-finder in the group. The release of relay I06disconnects starting conductor I05 from conductor I26 and from the lowerwinding of relay I06. The linefinder LF is now ready for use on anothercall.

What is claimed is:

1. The combination in a telephone system of a line having a plurality ofstations thereon, a register for each of said stations, anidentification device at one of said stations, means effective when acall is made on said line for testing the line for the presence of saiddevice, means dependent on the result of said test for selecting one ofsaid registers for operation, and means for testing said line todetermine whether said device is in operative condition.

2. The combination in a telephone system of a line having a plurality ofstations thereon, a register for each of said stations, anidentification device at one of said stations, means responsive to acall by any one of the stations on said line for testing the line todetermine the presence of said device, means dependent on the result ofsaid test for selecting one of said registers for operation, and meansto test said line after the calling party replaces his receiver todetermine whether said device is in operative condition.

3. The combination in a telephone system of a line having a plurality ofstations thereon, registers, one for each of said stations, anidentification device connected to the line at one of said stations,means controlled by the subscriber for disconnecting said device fromthe line, means for making a test of the line to determine the presenceor absence of said device, means dependent upon said test for selectingone of said registers foroperation, and means for testing said line todetermine whether said device is in operative condition.

l. In a telephone system, a line having a plurality of stations thereon,message registers, one for each of said stations, a space-dischargedevice at one of said stations, means effective when a call is made onsaid line for testing the line for the presence of said space-dischargedevice, means controlled as a result of said test for selecting one ofsaid registers for operation, and means for testing the line todetermine whether said space-discharge device is in Working condition.

5. In a telephone system, a line having a plurality of stations thereon,message registers, one for each of said stations, a gas-filled tubeconnected to the line at one of said stations, means controlled by thesubscriber for disconnecting said tube from the line, means responsiveto the initiation of a call on the line for testing said line todetermine whether or not said tube has been disconnected from the line,means controlled as a result of said test for selecting one of saidregisters, and means for subsequently testing said line to determinewhether the tube is in operative condition.

6. In a telephone system, a party line, registers, one for each party onsaid line, a spacedischarge tube connected to the line at one of saidstations, means controlled by the party at said station fordisconnecting said tube from the line, means effective when a call ismade at any one of said stations for testing the line to determinewhether or not said tube is connected to the line, means controlled bysaid test means for selecting one of said registers for operation, andmeans effective as a result of the replacement of the callingsubscribers receiver for again test ing said line to determine whethersaid tube is in working condition.

'7. In a telephone system, a subscribers line, a line relay therefore, amessage register for said line, an operating circuit for said registerincluding one of the talking conductors of the line, means for holdingthe line relay energized during conversation over said line, and meansfor releasing said line relay to close said operating circuit.

8. In a telephone system, a party line, a line relay therefor,registers, one for each of the parties on said line, an operatingcircuit for one of said registers including one of the talkingconductors of said line, means for holding the line relay energizedduring conversation, and means dependent on the station making the callfor releasing the line relay to close said operating circuit.

9. In a telephone system, a line having a plurality of stations thereon,a line relay for said line, a message register for one of said stations,an operating circuit for said register including the control conductorof said line, a second register ,for another of said stations, anoperating circuit for said second register including one of the talkingconductors of said line, means for holding the line relay in operatedcondition during the conversation period, and means for causing therelease of said relay to close the operating circuit of said secondregister.

HENRY I-IOVLAND.

